Ultraviolet transmittance (UVT) is a measurement of the amount of light having a certain wavelength, for example 254 nanometers, that passes through a length of a fluid. UVT values are generally provided as percentages of the amount of ultraviolet (UV) light that travels across the length of a fluid. UVT is affected by the amount of light energy that is absorbed and/or redirected by constituents in the fluid and may be expressed as a percentage of the light that passes through the fluid sample and is detected by a light sensor. For reference, distilled water having little or no constituents in the water has a UVT of almost 100%, while coffee may have a very low UVT, such as between 5-10%. Monitoring UVT for certain fluids, such as wastewater, may be important in determining suitability for consumption for example. However, accurate measurements may be difficult due to rapid fluid flow and fouling of equipment. Accordingly, alternative fluid diagnostic devices and methods may be desired.